There are Different Free Tools to use in SEO:1.Screaming Frog: The Screaming Frog SEO Spider allows you to quickly crawl, analyze and audit a site from an onsite SEO perspective and where you can easily miss a redirect, meta refresh or duplicate page issue.it is mainly for on page SEO.2.Webmaster Tool(Google Search Console): It allows webmasters to check indexing status and optimize visibility of their websites. 3.Keyword planner: Keyword Planner is totally free AdWords tool that helps to build Search Network campaigns by finding keyword ideas and estimating how they may perform.4.Google Analytics: Google analytic service offered by Google that tracks and reports website traffic.Free Moz Tool: The SEO Toolbar from Moz gives you quick access to many on-page SEO factors, Domain & Page Authority plus a quick no follow toggle.SEO quake: Same work as Moz Tool.Woorank: To check on page errors.You can create audit report with help of this.SEO site checkup: To check on page errors.Backlink watch: To check Backlink.Broken link check: To check broken link for the website.W3 validator: To check broken link for the website.Html validator:CSS validator:GTmetrix: It is a free tool that analyzes your page's speed performance. Using PageSpeed and YSlow, GTmetrix generates scores for your pages.